Rigid polyurethane foams

ABSTRACT

Polyol blend comprising a polyester polyol, a tertiary amine catalyst and an organic carboxylic acid wherein said carboxylic acid contains at least one OH, SH, NH 2  or NHR functional group, wherein R is an alkyl, cycloalkyl or aryl group and the use of said polyol blend in the manufacture of rigid polyurethane foams.

This invention relates to rigid polyurethane or urethane-modifiedpolyisocyanurate foams, to processes for their preparation and to polyolblends for use in said processes.

Rigid polyurethane and urethane-modified polyisocyanurate foams are ingeneral prepared by reacting a stoichiometric excess of polyisocyanatewith isocyanate-reactive compounds in the presence of blowing agents,surfactants and catalysts. One use of such foams is as a thermalinsulation medium in, for example, buildings.

Polyesther polyols or polyester polyols are generally used asisocyanate-reactive compounds.

Polyester polyols impart excellent flame retardancy characteristics tothe resulting polyurethane foams and are in some cases even lessexpensive than polyesther polyols.

There is a problem in respect of the stability of polyol blendscontaining polyester polyols and tertiary amine catalysts. It has beenproposed to solve this problem by adding an organic carboxylic acid(such as formic acid, acetic acid, 2-ethylhexanoic acid) to the polyolblend (see U.S. Pat. No. 4,758,605). In order to retain the reactivityover prolonged storage catalyst levels need to be increased. Whereas theinstability problem can be solved successfully in this way theprocessing of these systems is still uncontrollable which is reflectedin the rise profile of the rising foam when the polyol blend is reactedwith the polyisocyanate composition.

BRIEF SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide polyolblends containing polyester polyols and tertiary amine catalysts notshowing the disadvantages mentioned above.

DETAILED DESCRIPTION OF THE INVENTION

According to the present-invention polyol blends are provided comprisinga polyester polyol, a tertiary amine catalyst and an organic carboxylicacid wherein said carboxylic acid contains at least one OH, SH, NH₂, orNHR functional group, wherein R is an alkyl, cycloalkyl or aryl group.

The polyol blends of the present invention are stable for several weeks.Improved reaction profiles are obtained when these polyol blends areused to make rigid polyurethane foams; the cream time is decreased whileat the same time the expansion of the foam at string time is almostcomplete. Carboxylic acids to be used in the present invention have thegeneral formula X_(n)—R′—(CCOH)_(m) wherein X is OH, SH, NH₂or NHR, R′is an at least divalent hydrocarbon moiety, typically an at leastdivalent linear or branched aliphatic hydrocarbon moiety and/or an atleast divalent alicyclic or aromatic hydrocarbon moiety, n is an integerhaving a value of at least 1 and allows for mono and polyfunctionalsubstitution on the hydrocarbon moiety, m is an integer having a valueof at least 1 and allows for mono and polycarboxyl substitution on thehydrocarbon moiety.

The “at least divalent hydrocarbon moiety” can be a saturated orunsaturated moiety of 1 to 20 carbon atoms, including a linear aliphaticmoiety, a branched aliphatic moiety, an alicyclic moiety or an aromaticmoiety. Stated otherwise, R′ can, for example, be a linear or branchedalkylene group of 1 to 10 carbon atoms, a cyclic alkylene group of 4 to10 carbon atoms, or an arylene, an alkylene or an ararylene group of 6to 20 carbon atoms. Specific non-limiting examples of suitablehydrocarbon moieties are methylidene, ethylene, n-propylene,isopropylene, n-butylene, isobutylene, n-amylene, n-decylene,2-ethylhexylene, o-, m-, p-phenylene, ethyl-p-phenylene 2,5-naphthylene,p,p′-biphenylene, cyclopentylene, cyclopentylene, xylylene,1,4-dimethylenephenylene and the like. While above-noted radicals havetwo available substitution sites, at least one for a carboxyl group andone for a OH, SH, NH₂ or NHR group, it is contemplated that additionalhydrogen on the hydrocarbon could be replaced with further carboxyland/or OH, SH, NH₂or NHR groups.

The carboxylic ac ds useful in the practice of the present inventiongenerally have molecular weights below about 250.

The following carboxylic acids are illustrative of compounds suitablefor practicing the present invention: citric acid, dimethylolpropionicacid, bis-(hydroxymethyl)propionic acid, bishydroxypropionic acid,salicylic acid, m-hydroxy benzoic acid, p-hyidroxy benzoic acid,dihydroxybenzoic acid, glycolic acid, β-hydroxybutyric acid, cresoticacid, 3-hydroxy-2-naphthoic acid, lactic acid, tartaric acid, malicacid, resorcylic acid, hydroferulic acid, glycine, alanine,mercaptoacetic acid and the like.

Preferably X is OH, n is 1, R′ is a linear or branched aliphatichydrocarbon having 1 to 5 carbon atoms and m is 1, 2 or 3.Polycarboxylic acids are preferred. The hydroxyl group is preferably ina α or β position with respect to the carboxyl group.

Most preferred carboxylic acids are lactic acid, glycolic acid, malicacid and citric acid.

At least one of said carboxylic acids is used; mixture of two or more ofthese acids can be used as well.

Particularly preferred carboxylic acids for use in the present inventionare malic acid or a combination of malic acid and citric acid,preferably in a weight ratio of between 75:25 and 25:75, most preferablyin a weight ratio of about 1:1. Further improvements in reaction profileare observed.

The combination of malic acid and citric acid also leads to improvementsin other physical properties of the obtained foam such as compressionstrength and adhesion; also less variation in density distribution.

The carboxylic acid is generally used in an amount ranging from 0.1 to5% by weight based on the isocyanate-reactive composition, preferablyabout 1% to 3%

The term “polyester polyol” as used herein is meant to include anypolyester polyol having a hydroxyl functionality of at least two whereinthe majority of the recurring units contain ester linkages and themolecular weight is at least 400.

The polyester polyols for use in the present invention advantageouslyhave an average functionality of about 1.8 to 8, preferably about 2 to 6and more preferably about 2 to 2.5. Their hydroxyl number valuesgenerally fall within a range of about 15 to 750, preferably about 30 to550, more preferably 70 to 5:50 and most preferably about 200 to 550 mgKOH/g. The molecular weight of the polyester polyol generally fallswithin the range of about 400to about 10000, preferably about 1000 toabout 6000. Preferably the polyester polyols have an acid number between0.1 and 20 mg KOH/g; in general the acid number can be as high as 90 mgKOH/g.

The polyester polyols of the present invention can be prepared by knownprocedures from a polycarboxylic acid or acid derivative, such as ananhydride or ester of the polycarboxylic acid, and any polyhydricalcohol. The polyacid and/or polyol components may be used as mixturesof two or more compounds in the preparation of the polyester polyols.

The polyols can be aliphatic, cycloaliphatic, aromatic and/orheterocyclic. Low molecular weight, aliphatic polyhydric alcohols, suchas aliphatic dihydric alcohols having no more than about 20 carbon atomsare highly satisfactory. The polyols optionally may include substituentswhich are inert in the reaction, for example, chlorine and brominesubstituents, and/or may be unsaturated. Suitable amino alcohols, suchas, for example, monoethanolamine, diethanolamine, triethanolamine, orthe like may also be used. A preferred polyol component is a glycol. Theglycols may contain heteroatoms (e.g., thiodiglycol) or may be composedsolely of carbon, hydrogen and oxygen. They are advantageously simpleglycols of the general formula C_(n)H_(m) (OH)₂ or polyglycolsdistinguished by intervening ether linkages in the hydrocarbon chain, asrepresented by the general formula C_(n) H_(2n)O_(x) (OH)₂. Examples ofsuitable polyhydric alcohols include: ethylene glycol, propyleneglycol-(1,2) and -(1,3), butylene glycol-(1,4) and -(2,3),hexanediol-(1,6), octanediol-(1,8), neopentyl glycol,1,4-bishydroxymethyl cyclohexane, 2-methyl-1,3-propane diol, glycerin,trimethylolethane, hexanetriol-(1,2,6), butanetriol-(1,2,4), quinol,methyl glucoside, triethyleneglycol, tetraethylene glycol and higherpolyethylene glycols, dipropylene glycol and higher polybutyleneglycols, diethylene glycol, glycerol, pentaerythritol,trimethylolpropane, sorbitol, mannitol, dibutylene glycol and higherpolybutylene glycols. Especially suitable polyols are alkylene glycolsand oxyalkylene glycols, such as ethylene glycol, diethylene glycol,dipropylene glycol, triethylene glycol, tripropylene glycol,tetraethylene glycol, tetrapropylene glycol, trimethylene glycol,tetramethylene glycol and 1,4-cyclohexanedimethanol(1,4-bis-hydroxymethylcyclohexane).

The polycarboxylic acid component may be aliphatic, cycloaliphatic,aromatic and/or heterocyclic and may optionally be substituted, forexample, by halogen atoms and/or may be unsaturated. Examples ofsuitable carboxylic acids and derivatives thereof for the preparation ofthe polyester polyols include: oxsalic acid, malonic acid, adipic acid,glutaric acid, succinic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, phthalic acid, phthalic acid anhydride, terephthalicanhydride, isophthalic acid, terephthalic acid, trimellitic acid,tetrahydrophthalic acid anhydride, pyromellitic dianhydride,hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride,endomethylene tetrahydrophthalic anhydride, glutaric acid anhydride,malic acid, malic acid anhydride, terephthalic acid dimethylester,terephthalic acid-bis glycol ester, fumaric acid, dibasic and tribasicunsaturated fatty acids optionally mixed with monobasic unsaturatedfatty acids, such as oleic acids.

White the polyester polyols car. be prepared from substantially purereactant materials, more compiles ingredients can be used, such as theside-stream, waste or scrap residues from the manufacture of phthalicacid, terephthalic acid, dimethyl terephthalate, polyethyleneterephthalate, and the like. These compositions can be converted byreaction with polyols to polyester polyols through conventionaltransesterification or esterification procedures.

The production of the polyester polyols is accomplish ed by simplyreacting the polycarboxylic acid or acid derivative with the polyolcomponent in a known manner until the hydroxyl and acid values of thereaction mixture fall in the desired range. Alter transesterification oresterification the reaction product can optionally be reacted with analkylene oxide.

The term “polyester polyol” as used herein includes any minor amounts ofunreacted polyol remaining after the preparation of the polyester polyoland/or unesterified polyol (e.g., glycol) added after the preparation.The polyester polyol can advantageously include up to about 40% byweight free glycol. Preferably the free glycol content is from 2 to 30,more preferably from 2 to 15% by weight of the total polyester polyolcomponent.

Aliphatic and/or aromatic polyester polyols can be used according to thepresent invention.

Mixtures of two or more different polyester polyols can be used.

According to the present invention the polyester polyols described abovecan constitute the totality of the reactive mixture reacted with thepolyisocyanate; it is understood, however, that these polyols could alsobe used mixed with other isocyanate-reactive compounds conventionallyused in the art; preferably at least 10%, more preferably at least 20%by weight of the total isocyanate-reactive compounds are polyesterpolyols as described above.

The isocyanate-reactive compounds which can be employed in combinationwith the polyester polyols in the preparation of the rigid polyurethanefoams of the present invention include any of those known in the art forthat purpose. Of particular importance for the preparation of rigidfoams are polyols and polyol mixtures having average hydroxyl numbers offrom 300 to 1000, especially from 300 to 700 mg KOH/g, and hydroxylfunctionalities of from 2 to 8, especially from 3 to 8. Suitable polyolshave been fully described in the prior art and include reaction productsof alkylene oxides, for example ethylene oxide and/or propylene oxide,with initiators containing from 2 to 8 active hydrogen atoms permolecule. Suitable initiators include: polyols, for example glycerol,trimethylolpropane, triethanolamie, pentaerythritol, sorbitol andsucrose;. Polyamides, for example ethylene diamine, tolylene diamine,diarn-iodiphenylmethane and polymethylene polyphenylene polyamines; andaminoalcohols, for example ethanolamine and dlethanolamine; and mixturesof such initiators. Further suitable polymeric polyols include hydroxylterminated polythioethers, polyamides, pclyeszeramides, polycarbonates,polyacetals, polyolefins and polysiloxanes.

Any organic compound containing at least one nitrogen atom, preferably atertiary nitrogen atom and which is capable of catalysing thehydroxyl/isocyanate reaction can be used in the blends of the presentinvention.

Typical classes of tertiary amine catalysts include theN-alkylmorpholines, N-alkylalkanolamines, N,N-daikylcyclohexylamines andalkylamines where the alkyl groups are methyl, ethyl, propyl, butyl andthe like and isomeric forms thereof; and heterocyclic amines. Typicalbut not limiting thereof are triethvlenediamine,tetramethylethylenediamine, bis (2-dimethylaminoethyl)ether,triethylamine, tripropylamine, tributylamine, triamylamine, pyridine,quinoline, dimethylpiperazine, piperazine, N,N-dimethylcyclohexylamine,N-ethylmorpholine, 2-methylpiperazine, N,N-dimethylethanolamine,tetramethylpropanediamine, methyltriethylenediamine,2,4,6-tri(dimethylanomethyl)phenol,N,N′,N″-tris(dimethylaminopropyl)-symhexahydrotriazine, and the like,and mixtures thereof. Also amines containing isocyanate-reactive groupssuch as aminoalcohols can be used; examples hereof include2-(2-dimethylaminoethoxy)ethanol, trimethylamlnoethylethanolamine anddimethylethylethanolamine.

Preferred tertiary amine catalysts include triazines,dimethylbenzylamine, bis(dimethylaminoethyl)ether anddimethylcyclohexylamine. Especially dimorpholino diethylether,N-methylimidazole and dimethylamino pyridine are preferred; they furtherimprove the reaction profile.

The tertiary amine catalyst is generally present in proportions of fromabout 0.01 to about 10 pbw per 100 pbw of polyol. Preferably the amountof amine is from about 0.1 to about 5 pbw, most preferably from about0.2 to about 3 pbw per 100 pbw of polyol.

The blend of the present invention can also contain any of the blowingagents known in the art for the preparation of rigid polyurethane orurethane-modified polyisocyanurate foams. Such blowing agents includewater or other carbon dioxide-evolving compounds, or inert low boilingcompounds having a boiling point of above −70° C. at atmosphericpressure.

Where water as used as blowing agent, the amount may be selected inknown manner to orovide foams of the desired density, typical amountsbeing In the range from 0.05 to 5% by weight based on the total reactionsystem.

Suitable inert blowing agents include those well known and described inthe art, for example, hydrocarbons, dialkyl ethers, alkyl alkanoates,aliphatic and cycloaliphatic hydrofluorocarbons,hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons andfluorine-containing ethers.

Examples of preferred blowing agents include isobutane, n-pentane,isopentane, cyclotentane or mixtures thereof,1,1-dichloro-2-fluoroethane (HCFC 141b, 1,1,1-trifluoro-2-fiuoroethane(HFC 134a), chlorodifluoromethane (HCFC 22),1,1-difluoro-3,3,3-trifluoropropane (HFC 245fa) and blends thereof.

Particular mention may be made of blowing agent mixtures as described inPCT Patent Publication No. 96/12758, incorporated herein by reference,for manufacturing low density, dimensionally stable rigid foam. Theseblowing agent mixtures generally comprise at least 3 and preferably atleast 4 components of which preferably at least one is a (cyclo)alkane(preferably of 5 or 6 carbon atoms) and/or acetone.

The blowing agents are employed in an amount sufficient to give theresultant foam the desired bulk density which is generally-in the range15 to 70 kg/m³, preferably 20 to 50 kg/m³, most preferably 25 to 40kg/m³. Typical amounts of blowing agents are in the range 2 to 25% byweight based on the total reaction system.

When a blowing agent has a boiling point at or below ambient it ismaintained under pressure until mixed with the other components.Alternatively, it can be maintained at subambient temperatures untilmixed with the other components.

Other optional additives for the polyol blends of the present inventioninclude crosslinking agents, for examples low molecular weight polyolssuch as triethanolamine, processing aids, viscosity reducers, dispersingagents, plasticizers, mold release agents, antioxidants, fillers (e.g.carbon black), cell size regulators such as insoluble fluorinatedcompounds (as described, for example, in U.S. Pat. No. 4,981,879, U.S.Pat. No. 5,034,424, U.S. Pat. No. 4,972,002, EP 0508649, EP 0498628, WO95/18176), non-amine polyurethane catalysts (e.g. stannous salts ofcarboxylic acids), trimerisation catalysts (e.g. alkali metal carboxylicacid salts), surfactants such as polydimethylsiloxane-polyoxyalkyleneblock copolymers and non-reactive and reactive fire retardants, forexample haogenated alkyl phosphates sucn as tris chloropropyl phosphate,triethylphosphate, diethylethylphosphonate anddimethylmethylphosphonate. The use of such additives is well known tothose skilled in the art.

Suitable organic polyisocyanates to se reacted with the polyol blends ofthe present invention to form rigid polyurethane or urethane-modifiedpolyisocyanurate foams include any of those known in the art for thepreparation of rigid polyurethane or urethane-modified polyisocyanuratefoams, and in particular the aromatic polyisocyanates such asdiphenylmethane diusocyanate in the form of its 2,4′-, 2,2′- and4,4′-isomers and mixtures thereof, the mixtures of diphenylmethanediisocyanates (MDI) and oligomers thereof known in the art as “crude” orpolymeric MDI (polymethylene polyphenylene polyisocyanates) having anisocyanate functionality of greater than 2, toluene diisocyanate in theform of its 2,4- and 2,6-isomers and mixtures thereof, 1,5-naphthalenediisocyanate and 1,4-diisocyanatobenzene. Other organic polyisocyanateswhich may be mentioned include the aliphatic diisocyanates such asisophorone diisocyanate, 1,6-disocyanatohexane and4,4′-diisocyanatodicyclohexylmethane. Further suitable polyisocyanatesfor use in the process of the present invention are those described inEP-A-0320134.

Modified polyisocyanates, such as carbodiimide or uretonimine modifiedpolyisocyanates can also be employed.

Still other useful organic polyisocyanates are isocyanate-terminatedprepolymoers prepared by reacting excess organic polyisocyanate with aminor amount of an active hydrogen-containing compound.

Preferred polyisocyanates to be used in the present invention are thepolymeric MDI's.

The quantities of the polyisocyanate composition and the polyfunctionalisocyanate-reactive composition to be reacted can be readily determinedby the man skilled in the art. In general the NCO:OH ratio falls withinthe range 0.85 to 1.40, preferably about 0.95 to 1.20. Also higherNCO:OH ratios (for example, up to 3.0) fall within the presentinvention.

In operating the process for making rigid foams according to theinvention, the known one-shot, prepolymer or semi-prepolymer techniquesmay be used together with conventional mixing methods and the rigid foammay be produced in the form of slabstock, mouldings, cavity fillings,sprayed foam, frothed foam or laminates with other materials such ashardboard, plasterboard, plastics, paper or metal.

According to one embodiment of the present invention the polyol blend asdescribed above is reacted with a polylsocyanate composition to makerigid polyurethane foams.

According to another embodiment of the present invention the ingredients(polyester polyol, amine catalyst and carboxylic acid) are not added asa blend but are added separately to the reaction mixture.

The foams of the present invention are advantageously used for producinglaminates whereby the foam is provided on one or both sides with afacing sheet. The laminates can be made in a continuous or discontinuousmanner by depositing the foam-forming mixture on a facing sheet andpreferably placing another facing sheet on the deposited mixture. Anyfacing sheet previously employed to produce building panels can beemployed and can be of a rigid or flexible nature.

The various aspects oil this invention are illustrated, but not limitedby the following examples in which the following ingredients are used:

Polyol A: a sorbitol initiated polyester polyol of OH value 460 mgKOH/g.

Polyol B: an aliphatic polyester polyol of OH value 356 mg KOH/g andacid value 0.5 mg KOH/g.

Polyol C: an aromatic amine initiated polyester polyol of OH value 495mg KOH/g.

Polyol D: a brominated polyester polyol of OH value 310 mg KOH/g.

Polyol E: an aromatic polyester polyol of OH value 240 mg KOH/g.

Polyol F: an aromatic polyester polyol of OH value 350 mg KOH/g.

Fire retardant A: a chlorinated flame retardant.

Fire retardant B: a phosphorus based flame retardant.

Surfactant: a silicone surfactant.

DMBA: dimethylbenzylamine catalyst available from Protex.

DMDEE: dimorpholinodiethylether catalyst available from Nitroil.

DMAP: dimethylaminopyridine catalyst available from Aldrich.

NMI: N-methyl imidazole catalyst available from BASF.

Polycat 41: tris(dimethylaminopropyl)hexahydrotriazine catalystavailable from Air Products.

Niax Al: bis(dimethylaminoethyl)ether catalyst available from OSi.

Texacat DP914: a catalyst available from Texaco.

DMCHA: dimethylcyclohexylamine catalyst available from BASF.

SUPRASEC DNR: polymeric MDI available from Imperial Chemical Industries.

SUPRASEC is a trademark of Imperial Chemical Industries.

EXAMPLE 1

Rigid polyurethane foams were made from a polyol composition and apolyisocyanate composition containing the ingredients listed below inTable 1 at an NCO index of 1.15.

The reaction profile was followed in respect of cream time (time takenfor the reaction mixture to start foaming) and string time (time takenfor the reaction mixture to reach the transition point from fluid tocross-linked mass). The height of expansion was measured at the stringtime and also at the end of rise of the foam; from those two figures theexpansion factor at srtring time (height at string/height at end ofrise) was determined.

The results are also given in Table 1.

The rise profile was also followed by Dynamic Flow Data analysis.Results are presented in FIGS. 1, 2 and 3 expressing the height of therising foam versus the reaction time.

These results show that whereas acetic acid leads to delayed actioncatalysis (Foam No. 2) addition of functionalised carboxylic acids ofthe present invention improves the reaction profile (Foam No. 3) (seeFIG. 1). Addition of selected classes of catalysts (for example, DMDEE,DMAP, NMI, Texacat DP914) (Foams No. 4, 5, 6, 7, 9) further improves thereaction profile (see FIG. 2).

Glycolic acid (Foam No. 9) performs better than lactic acid (Foam No. 4)in terms of reaction profile improvement (see FIG. 3).

TABLE 1 Foam No. 1 2 3 4 5 6 7 8 9 POLYOL Polyol A pbw 20.5 20.5 20.520.5 20.5 20.5 20.5 20.5 20.5 Polyol B pbw 23.0 23.0 23.0 23.0 23.0 23.023.0 23.0 23.0 Polyol C pbw 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0Polyol D pbw 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 acetic acidpbw 1.0 glycolic acid pbw 1.0 lactic acid pbw 1.1 1.1 1.1 1.1 1.1 1.1Fire retardant A pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Fire retardantB pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 Surfactant pbw 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 DMBA pbw 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 DMDEEpbw 1.5 1.5 DMAP pbw 0.3 NMI pbw 0.3 Polycat 41 pbw 0.7 Niax A1 pbw 0.15Texacat DP914 pbw 0.5 DMCHA pbw 0.80 0.80 0.80 water pbw 3.3 3.3 3.3 3.33.3 3.3 3.3 3.3 3.3 HCFC 141b pbw 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2 4.2POLYISOCYANATE SUPRASEC DNR pbw 139 139 139 139 139 139 139 139 139Cream time sec 17 18 16 17 20 16 17 18 13 String time sec 154 162 128120 134 131 141 137 127 Expansion factor % 93 56 79 89 90 86 90 84 95 atstring time

EXAMPLE 2

The stability of the polyol blend of Foam No. 1 and Foam No. 3 (asidentified above in Table 1) was determined by measuring cream time,string time and density of the foam prepared initially and after storageof the polyol blend for 3 days, 1 week and 3 weeks, respectively, at 40°C.

The results are presented in Table 2 for Foam No. 1 and in Table 3 forFoam No. 3.

TABLE 2 Foam No. 1 Cream time (sec) String time (sec) Density (g/l)Initial 17 154 27.6 After 3 days 18 185 28.0 After 1 week 20 245 29.0After 3 weeks 24 267 29.6

TABLE 3 Foam No. 3 Cream time (sec) String time (sec) Density (g/l)Initial 23 152 27.8 After 3 days 24 155 28.2 After 1 week 23 160 28.3After 3 weeks 24 161 28.1

These results show that whereas there are relatively large variations incream time, string time and density for Foam No. 1, these differencesare only marginal for Foam No. 3. Thus stability of the polyol blendscontaining the functionalised carboxylic acids of the present inventionis improved compared to polyol blends not containing said aclos.

EXAMPLE 3

Rigid polyurethane foams were made from a polyol composition and apolyisocyarate composition containing the ingredients listed below inTable 4 at an NCO index of 1.15.

The reaction profile was followed in respect of crear time (time takenfor the reaction mixture to start foaming) and string time (time takenfor the reaction mixture to reach the transition point from fluid tocross-linked mass). The height of expansion was measured at the stringtime and also at the end of rise of the foam; from those two figures theexpansion factor at string time (height at string/height at end of rise)was determined.

The results are also given in Table 4.

It is to be noted that using citric acid or malic acid leads to thelowest density foam.

EXAMPLE 4

Rigid polyurethane foams were made from a polyol composition and apolyisocyanate composition containing the ingredients listed below inTable 5 at an NCO index of 1.15.

The reaction profile was followed in respect of cream time (time takenfor the reaction mixture start foaming) and string time (time taken forthe reaction mixture to reach the transition point from fluid tocross-linked mass). The height of expansion was measured at the stringtime and also at the end of rise of the foam; from those two figures theexpansion factor at string time (height at string/height at end of rise)was determined.

The results are also given in Table 5.

The rise profile was also followed by Dynamic Flow Data analysis.Results are presented in FIG. 4 expressing the height of the rising foamversus the reaction time for Foams Nos 18, 19 and 20.

These results show that further improvements in reaction profile areobtained when malic acid (Foam No. 19) or a combination of malic acidand citric acid (Foam No. 20) are used instead of lactic acid (Foam No.18).

TABLE 4 Foam No. 10 11 12 13 14 15 16 17 POLYOL Polyol A pbw 20.5 20.520.5 20.5 20.5 20.5 20.5 20.5 Polyol B pbw 23.0 23.0 23.0 23.0 23.0 23.023.0 23.0 Polyol C pbw 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Polyol Dpbw 21.0 21.0 21.0 21.0 21.0 21.0 21.0 21.0 Lactic acid pbw 1.1 Tartaricacid pbw 1.1 4-Hydroxybenzoic acid pbw 1.1 Citric acid pbw 1.1 Salicylicacid pbw 1.1 Malic acid pbw 1.1 Glycolic acid pbw 1.1Bis(hydroxymethyl)propionic acid pbw 1.1 Fire retardant A pbw 8.3 8.38.3 8.3 8.3 8.3 8.3 8.3 Fire retardant B pbw 8.3 8.3 8.3 8.3 8.3 8.3 8.38.3 Surfactant pbw 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 DMBA pbw 1.0 1.1 0.51.0 1.25 0.6 0.8 0.5 DMDEE pbw 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 water pbw3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 HCFC 141b pbw 4.2 4.2 4.2 4.2 4.2 4.24.2 4.2 POLYISOCYANATE SUPRASEC DNR pbw 139 139 139 139 139 139 139 139Density kg/m³ 30.9 32.6 33.1 30.5 32.1 30.8 31.8 32.5 Cream time sec 2016 19 20 23 17 34 21 String time sec 110 113 107 103 107 110 125 110Expansion factor % 92 88 92 92 92 92 84 89 at string time

TABLE 5 Foam No. 18 19 20 21 22 POLYOL Polyol A pbw 20.5 20.5 20.5 20.520.5 Polyol B pbw 23.0 23.0 23.0 23.0 23.0 Polyol C pbw 10.0 10.0 10.010.0 10.0 Polyol D pbw 21.0 21.0 21.0 21.0 21.0 Lactic acid pbw 1.1Malic acid pbw 1.0 0.5 0.25 0.75 Citric acid pbw 0.5 0.75 0.25 Fireretardant A pbw 8.3 8.3 8.3 8.3 8.3 Fire retardant B pbw 8.3 8.3 8.3 8.38.3 Surfactant pbw 2.0 2.0 2.0 2.0 2.0 DMBA pbw 1.0 0.6 0.7 0.66 0.79DMDEE pbw 1.5 1.5 1.5 1.5 1.5 water pbw 3.3 3.3 3.3 3.3 3.3 HCFC 141bpbw 4.2 4.2 4.2 4.2 4.2 POLYISOCYANATE SUPRASEC DNR pbw 139 139 139 139139 Cream time sec 20 13 13 17 13 String time sec 108 108 104 102 104Expansion factor at % 91.4 90.1 92.4 92.2 91.7 string time

EXAMPLE 5

The stability of the polyol blend of Foam No. 19 and Foam No. 20 (asidentified above in Table 5) was determined by measuring cream time,string time and density of the foam prepared initially and after storageof the polyol blend for 1 day, 4 days, 1 week and 2, 3, 4 and 5 weeks,respectively, at 40° C.

The results are presented in Table 6 for Foam No. 19 and in Table 7 forFoam No. 20.

TABLE 6 Foam No. 19 Cream time (sec) String time (sec) Density (g/l)Initial 12 107 30.4 After 1 day 15 111 30.3 After 4 days 15 115 31.3After 1 week 15 113 31.6 After 2 weeks 15 112 31.4 After 3 weeks 15 11731.7 After 4 weeks 14 115 31.1 After 5 weeks 15 118 30.8

TABLE 7 Foam No. 20 Cream time (sec) String time (sec) Density (g/l)Initial 12 106 30.8 After 1 week 15 106 30.3 After 2 weeks 15 108 30.3After 4 weeks 15 110 31.2 After 5 weeks 15 108 30.1

EXAMPLE 6

Rigid polyurethane foams were made from a polyol composition and apolyisocyanate composition containing the ingredients listed below inTable 8 at an NCO index of 1.

The reaction profile was followed in respect of cream time (time takenfor the reaction mixture to start foaming) and string time (time takenfor the reaction mixture to reach the transition point from fluid tocross-linked mass). Free rise density was also determined.

The results are also given in Table 8.

TABLE 8 Foam No. 23 24 25 POLYOL Polyol A pbw 21.4 21.4 21.4 Polyol Bpbw 34.0 Polyol C pbw 11.7 11.7 11.7 Polyol D pbw 11.0 11.0 11.0 PolyolE pbw 34.0 Polyol F pbw 34.0 Lactic acid pbw 1.1 1.1 1.1 Fire retardantB pbw 13.5 13.5 13.5 Surfactant pbw 1.8 1.8 1.8 DMBA pbw 1.2 1.1 1.0DMDEE pbw 0.9 0.8 0.9 water pbw 3.4 3.4 3.4 HFC 134a pbw 4.0 4.0 4.0POLYISOCYANATE SUPRASEC DNR pbw 140 126 140 Cream time sec 7 7 6 Stringtime sec 95 91 95 Free rise density kg/m³ 27.6 27.3 28.0

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows rise profiles of foams 1, 2, and 3 over time.

FIG. 2 shows rise profiles of foams 3 and 4 over time.

FIG. 3 shows rise profiles of foams 4 and 9 over time.

FIG. 4 shows rise profiles of foams 18, 19, and 20 over time.

What is claimed is:
 1. An isocyanate-reactive composition comprising:(i) at least 10 wt %, relative to the total weight ofisocyanate-reactive compounds, of a polyester polyol having an averagefunctionality of from 1.8 to 8, a hydroxyl number of from 15 to 750 mgKOH/g, and a molecular weight of 400 to 10,000; (ii) 0.1-5 wt %,relative to the total weight of the isocyanate-reactive composition, ofan amine catalyst; (iii) 0.1-5 wt %, relative to the total weight of theisocyanate-reactive composition, of at least one carboxylic acidrepresented by the formula HO—R′—(COOH)_(m), wherein R′ represents alinear or branched aliphatic hydrocarbon having 1 to 5 carbon atoms, andm represents the value 1, 2, or 3; and (iv) a blowing agent.
 2. Anisocyanate-reactive composition comprising: (i) a polyester polyol; (ii)an amine catalyst; and (iii) 0.1-5 wt %, relative to the total weight ofthe isocyanate-reactive composition, of at least one carboxylic acidrepresented by the formula X_(n)—R′—(COOH)_(m), wherein X represents OH,SH, NH₂, or NHR, R′ represents an at least divalent hydrocarbon moiety,n and m individually represent an integer having a value of at least 1,and R represents an alkyl, cycloalkyl, or aryl group. 3.Isocyanate-reactive composition according to claim 1 wherein saidcarboxylic acid is selected from the group consisting of lactic acid,glycolic acid, malic acid, citric acid.
 4. Isocyanate reactivecomposition according to claim 3, wherein said carboxylic acid is amixture of citric acid and malic acid at a weight ratio of about 1:1. 5.Isocyanate-reactive composition according to claim 1 wherein said aminecatalyst is a tertiary amine selected from the group consisting ofN-alkylmorpholine, N-alkylalkanolamine, N,N-dialkylcyclohexylamine,alkylamine, heterocyclic amine.
 6. Isocyanate-reactive compositionaccording to claim 5 wherein said amine catalyst is dimorpholinodiethylether or N-methylimidazole or dimethylamino pyridine or atriazine.
 7. The isocyanate-reactive composition according to claim 1,wherein said at least one carboxylic acid is present to stabilize saidcomposition. 8.The isocyanate-reactive composition according to claim 2,wherein said at least one carboxylic acid is present to stabilize saidcomposition.